Conventional electrical capital producing machines, such as computer numerically controlled (CNC) machines, lathes, and other shop machines, typically receive alternating current (AC) power from a power supply, such as an electrical outlet, through a pair of conducting lines. The pair of conducting lines, often referred to as the line and neutral conductors, enable the electrical appliance, or load, to receive the current necessary to operate.
However, fire is a very valid concern in any machining facility. Fires occurring in machines running oil-based coolant can cause significant damage in seconds and potentially spread throughout the facility causing extensive damage. Even in the presence of operators, machines have been completely destroyed.
Fire protection of CNC and other machine tools is critically important as there is a great risk of fire in these valuable machines. Fires can quickly cause expensive down time, costly repairs, possible human injury and damage to plant and equipment. The number of CNC machines throughout the world has grown dramatically as they have become established as state-of-the-art equipment for milling, drilling, grinding, tapping, honing, turning and other operations critical to manufacturing. These machines can cost up to $300,000 each, and are designed to run in a demanding, often grueling work environment. Fires in CNC machines are commonplace. Using oil-based coolants, typically combustible petroleum or mineral oil, flash fires are reported as a “fireball” when oil mist is ignited. These machine fires can be catastrophic to the operator and result in significant downtime and expensive property damage.
In other environments, appliances such as, for example, dehumidifiers, refrigerators, air conditioners, and the like, can overheat to the point of causing a fire if AC power is continued to be applied after a mechanical failure, e.g., refrigerant leakage.
Typical fire suppressant systems detect a fire after it has started and release a fire-suppressant agent, such as, for example, CO2. However, these typical fire suppressant systems operate after the fire has started and do not disconnect the power from the burning machine. In other words, the machine is still electrically hot during the fire and even after the fire is suppressed. Thus, posing a potentially life threatening hazard to the operator as well as continuing to reignite the fire.
Oftentimes vibration measurement is used as a tool to determine the condition of different types of production machinery. Vibration measurement is used on equipment that has rotating parts, for example, pumps, turbines and fans and is often used in predictive maintenance programs. Moreover, excessive vibrations are often prelude to a catastrophic mechanical failure and/or fire.
In other environments where compressors are employed, such as in air conditioners or dehumidifiers there is also a risk of fire if the compressor malfunctions, leaks refrigerant, or is otherwise operated incorrectly. In these situations a compressor may overheat to the point where electrical insulation begins to deteriorate leading to electrical arcing between wires and/or other conductive surfaces. Often times this leads to a catastrophic fire. Traditional arc detector circuits typically detect arcing after arcing has begun which may not provide sufficient protection.
Thus, there exists a need for an apparatus that can sense a potentially dangerous condition and interrupt AC power to the machine and provide a warning early in the breakdown process.